1. Field of the Invention
The present invention relates, in general, to a method of tracing the geometry of a track immediately ahead of a ballast pick-up device, with respect to a working direction, and of restoring said geometry after it has been destroyed by the operation of said ballast pick-up device. The invention also relates to a machine for cleaning ballast.
2. Description of Related Art
A method of the afore-mentioned type is known from U.S. Pat. No. 4,574,704. When a ballast cleaning machine excavates the ballast underneath a track, the track geometry is necessarily destroyed. Restoring that geometry after introducing the cleaned ballast is problematic. According to the prior art method, the position of a first measuring chord—situated ahead of the ballast pick-up device with regard to the working direction—follows the track geometry. This position is used as a reference to guide a second, trailing measuring chord. To that end, a vector height of the first measuring chord is measured, and an angle enclosed by the two measuring chords is recorded. A track lifting device then displaces the track in the transverse direction until a rear end point of the second measuring chord, after the angle has been attained, comes to lie in the desired position. That method, however, is applicable only in a track curve. For working in transition curves, a correction factor must be taken into account.